Semiconductor device, method for manufacturing semiconductor device and gas for plasma cvd

ABSTRACT

The present invention relates to a semiconductor device comprising an insulation film consisting of a fluoridation carbon film that has been subjected to thermal history of 420° C. or lower. The feature of the present invention is that an amount of hydrogen atoms included in the fluoridation carbon film is 3 atomic % or less before the fluoridation carbon film is subjected to the thermal history.

FIELD OF THE INVENTION

This invention relates to a semiconductor device including an insulationfilm consisting of fluoridation carbon film (fluorocarbon film), such asan interlayer insulation film, and to a manufacturing method of thesemiconductor device.

In addition, this invention relates to a gas for a plasma CVD processwhich is useful in the manufacturing method of the semiconductor device.

BACKGROUND ART

As one way for achieving higher integration of a semiconductor device,there is a technique in which wirings are formed in a multi-layeredmanner. In order to adopt a multi-layered wiring structure, an n-thwiring layer and an (n+1)-th wiring layer are connected via a conductivelayer, and a thin film called an interlayer insulation film is formed atan area except for the conductive layer. As a typical example of theinterlayer insulation film, there is known an SiO₂ film. However,recently, in order to achieve much higher speed for operation of adevice, it has been required to further decrease the dielectric constantof the interlayer insulation film.

In view of such requirement, a fluoridation carbon film that is achemical compound of carbon (C) and fluorine (F) has been paid attentionto. While a dielectric constant of the SiO₂ film is around 4, adielectric constant of the fluoridation carbon film can be not higherthan 2 if a kind of source gas is suitably selected. Thus, thefluoridation carbon film is a much effective film as an interlayerinsulation film. Various gases are known as a source gas for thefluoridation carbon film (Japanese Patent Laid-Open Publication No.144675/1998: section O017). For example, a C₅F₈ (octafluorocyclopentene)gas is a superior source gas because it can form a film having a networkstructure.

In addition, as a conventional art relating to the source gas for thefluoridation carbon, there is known a technique disclosed in JapanesePatent Laid-Open Publication No. 237783/1997. According to thetechnique, hexafluoro-1,3-butadiene or hexafluoro-2-butyne is used as asource gas, and an insulation film consisting of a fluorinated amorphouscarbon is formed by means of a plasma CVD method, so that a dielectricconstant of 2.1 or 2.5 can be respectively obtained.

According to Japanese Patent Laid-Open Publication No. 220668/2002,various unsaturated carbon fluorides are used as a film-forming gas, andfilm density and film surface roughness are studied.

According to Japanese Patent Laid-Open Publication No. 332001/2000, bymeans of a plasma CVD method using a high-purity octafluorocyclopentene,a film having a dielectric constant of 2.4 can be obtained.

SUMMARY OF THE INVENTION

In the source gas for the fluoridation carbon film, a small amount ofhydrogen is included, for example, atomic % in the 10⁻² order ofhydrogen is included. Herein, the atomic % in the source gas means avalue calculated considering C₅F₈ as an atom. The small amount ofhydrogen may be thought to be hydrogen that has mainly formed water leftin the source gas without completely removed.

On the other hand, when the fluoridation carbon film is formed by usingthe C₅F₈ gas including the small amount of hydrogen, an amount ofhydrogen included in the film is 5 atomic %, for example. That is,although the amount of hydrogen included in the source gas is verysmall, the amount of hydrogen included in the film is not so small. Thereason is thought that an atom of the hydrogen in the source gas mayselectively combine with dangling-bond of the fluorine in the film.

However, when the hydrogen is included in the fluoridation carbon film,the hydrogen may bond the fluorine to generate hydrogen fluoride. Then,when it is heated to 350° C. or higher, for example, during amanufacturing step of a device, the hydrogen fluoride may go off fromthe film. As a result, weight reduction of the fluoridation carbon filmmay be caused. That is, if hydrogen is included in the source gas, thefluoridation carbon film may be inferior in thermal stability. Then, ifdegassing is caused during a heating step, the film may be cavitated tobecome weaker, so that adhesion is deteriorated, holding action of thewirings by the interlayer insulation film is also deteriorated, andwinding of the wirings and/or electro-migration may be generated moreeasily. In addition, there is a fear that the wirings may be corroded bythe hydrogen fluoride.

This invention is intended to solve the above problems. The object ofthis invention is to provide a semiconductor device including aninsulating film consisting of a good fluoridation carbon film. Inaddition, the object of the invention is to provide a manufacturingmethod of a semiconductor device that can form an insulation filmsuperior in thermal stability, in forming an insulating film consistingof a fluoridation carbon film by using a source gas consisting of achemical compound of carbon and fluorine.

A semiconductor device of the present invention comprises an insulationfilm consisting of a fluoridation carbon film that has been subjected tothermal history of 420° C. or lower, for example 350° C. to 420° C.,wherein an amount of hydrogen atoms included in the fluoridation carbonfilm is 3 atomic % or less before the fluoridation carbon film issubjected to the thermal history. The insulation film is an interlayerinsulation film, for example.

In general, if hydrogen atoms are included in the fluoridation carbonfilm, the hydrogen and the fluorine may react on each other to becomehydrogen fluoride and to go off from the film (to cause degassing),during a heating step conducted afterward. However, according to theinvention, since the amount of hydrogen atoms included in thefluoridation carbon film is 3 atomic % or less before the fluoridationcarbon film is subjected to the thermal history of 420° C. or lower,such as thermal history of 350° C. to 420° C., weight reduction of thefluoridation carbon film when the fluoridation carbon film is subjectedto the thermal history may be restrained. Thus, functional deteriorationof the fluoridation carbon film as an insulation film may be restrained.

In addition, the invention is a manufacturing method of a semiconductordevice comprising the steps of: generating a plasma of a source gasconsisting of a chemical compound of carbon and fluorine and includinghydrogen atoms of 1×10⁻³ atomic % or less; and forming an insulatingfilm consisting of a fluoridation carbon film that includes hydrogenatoms of 3 atomic % or less, on a substrate, by using the plasma of thesource gas.

According to the above feature, since the source gas consisting of achemical compound of carbon and fluorine and including hydrogen atoms of1×10⁻³ atomic % or less is used, it is possible to obtain the insulatingfilm consisting of a fluoridation carbon film that includes hydrogenatoms of 3 atomic % or less.

Herein, the amount represented by the unit of atomic % regarding thehydrogen atoms in the source gas means an amount calculated byconsidering the chemical compound of carbon and fluorine as one atom.Even if the other atoms such as oxygen atoms are included in the sourcegas besides the hydrogen atoms, since the amount of such impurities (theother atoms) is very small, the amount represented by the above unit,which means a ratio of the number of hydrogen atoms with respect to thenumber of molecules of the chemical compound, is used.

On the other hand, the unit of atomic % regarding the hydrogen atoms inthe insulation film means an amount representing a ratio of the hydrogenatoms with respect to the total number of the respective atoms, forexample the total number of the carbon atoms, the fluorine atoms and thehydrogen atoms.

Preferably, the manufacturing method of a semiconductor device furthercomprises a step of heating the substrate at a temperature of 420° C. orlower, for example a temperature of 350° C. to 420° C., after the stepof forming the insulating film.

In addition, for example, the chemical compound of carbon and fluorineis C₅F₈.

On the other hand, by means of a method using a conventional gas for aCVD process, it was impossible to obtain an interlayer insulation filmhaving a small dielectric constant, which has a sufficient effect onreduction of capacity between wirings in a highly-integratedsemiconductor device.

The object of the present invention is to provide a gas for a plasma CVDprocess, used for manufacturing an interlayer insulation film having asmall dielectric constant.

The inventors studied and studied to achieve the above object. Finally,they have found that the amount of a chemical compound including ahydrogen atom in a gas for a plasma CVD process has a great effect oncharacteristics of a film formed by the plasma CVD process, and thatgeneration of a corrosion gas during a heating process of the formedfilm is restrained if the amount of a chemical compound including ahydrogen atom in a gas for a plasma CVD process is restrained, so thatthe present invention was completed.

Then, the present invention provides a gas for a plasma CVD processcontaining an unsaturated carbon fluoride compound and a chemicalcompound including a hydrogen atom, the amount of the chemical compoundincluding a hydrogen atom being 90 weight ppm or less.

Herein, it is preferable that the gas for a plasma CVD process furthercontains water in the amount of 3 weight ppm or less.

Especially, it is preferable that the unsaturated carbon fluoridecompound is octafluorocyclopentene, octafluoro-2-pentyne, orhexafluoro-1,3-butadiene.

In addition, it is preferable to manufacture the gas for a plasma CVDprocess by bringing a composition of the unsaturated carbon fluoridecompound and the chemical compound including a hydrogen atom in contactwith burned adsorbent.

In addition, the present invention provides a forming method of aninsulation film comprising the step of conducting a plasma CVD processby using the above gas.

When the gas for a plasma CVD process according to the present inventionis used to conduct the plasma CVD process, it is possible toreproducibly form an interlayer insulation film having a smalldielectric constant, which has a sufficient effect on reduction ofcapacity between wirings of a highly-integrated semiconductor device,and it is also possible to obtain a remarkable effect that no corrosiongas is generated even when a semiconductor tip having the interlayerinsulation film formed by using the gas for a plasma CVD process issubjected to a heating process during manufactuning step of asemiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing a state wherein a fluoridationcarbon film is formed according to an embodiment of the presentinvention;

FIG. 2 is a sectional view showing a semiconductor device manufacturedby the embodiment of the present invention;

FIG. 3 is a longitudinal side view showing an example of a plasmafilm-forming apparatus used for the embodiment of the present invention,together with a partial sectional view thereof;

FIG. 4 is a plan view showing a second gas-supplying part of the plasmafilm-forming apparatus of FIG. 3;

FIG. 5 is a perspective view showing an antenna part of the plasmafilm-forming apparatus of FIG. 3, together with a partial sectional viewthereof; and

FIG. 6 is a graph comparing relationships between heating temperaturesof the fluoridation carbon film and weight reduction thereof based ondifference of the amount of hydrogen in a source gas.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A manufacturing method of a semiconductor device according to theinvention includes a step of forming an insulation film consisting of afluoridation carbon film (CF film). An embodiment is explained, whereinan interlayer insulation film is formed as an insulation film.

FIG. 1 is a view showing an image of the embodiment. As a substrate 1, asubstrate for forming an integrated circuit, for example including aCMOS, is used. For example, a substrate is used wherein a BPSG film 11has been formed on a surface thereof. The BPSG film 11 means a silicateglass film into which boron (B) and phosphorus (P) have been doped.Instead of the BPSG film 11, a silicon oxide film may be used, which maybe formed from TEOS as a source.

As a source gas 2, a chemical compound of carbon and fluorine such asC₅F₈ is used. It is necessary that the amount of hydrogen atoms includedin the C₅F₈ gas is 1×10⁻³ atomic % or less.

When the C₅F₈ gas is made into a plasma, active species of the chemicalcompound of carbon and fluorine included in the plasma are deposited ona surface of the substrate 1, so that a fluoridation carbon film 3 isdeposited. At that time, the hydrogen included in the source gas iscaptured in the fluoridation carbon film 3. As described above, thehydrogen atoms selectively combine with dangling-bond of fluorine atomsin the fluoridation carbon film 3. Thus, the amount of the hydrogencaptured in the fluoridation carbon film 3 becomes larger than a contentratio thereof in the source gas.

If the C₅F₈ gas including the hydrogen atoms of 1×10⁻³ atomic % or lessis used to conduct a plasma process as described below, it is possibleto restrain the amount of the hydrogen captured in the fluoridationcarbon film 3 to 3 atomic % or less. The value is based on examples,which are described below. The amount of the hydrogen atoms included inthe source gas is obtained by a calculation from a measured value ofwater content included in the source gas. In direct definition by thewater content, the water content included in the source gas ispreferably 0.5 weight ppm or less (then, a calculated value of thehydrogen atoms included in the source gas is 1.17×10⁻³ atomic % orless), more preferably 0.1 weight ppm or less.

FIG. 2 is an example of a semiconductor device including an interlayerinsulation film, which has been formed as described above. 41 representsa p-type silicon layer, 42 and 43 represent n-type portions respectivelyserving as a source and a drain, 44 represents a gate oxide film and 45represents a gate electrode. A MOS transistor is formed by theseelements. In addition, 46 represents a BPSG film, 47 represents a wiringmade of, for example, tungsten (W), and 48 represents a side spacer. Aplurality of interlayer insulation films 52 (two films in FIG. 2 for theconvenience) is layered in a multi-layered structure on the BPSG film46, a wiring layer 52 made of, for example, copper having been buried ineach interlayer insulation film 52. Herein, 53 represents a hard maskmade of, for example, silicon nitride, 54 represents a protection layermade of, for example, a titanium nitride or a tantalum nitride, forpreventing diffusion of the wiring metal, and 55 represents a protectionfilm.

The manufacturing process of the semiconductor device includes a step ofheating the substrate. Thus, the interlayer insulation films 52 areheated to a process temperature of the heating step. As an example ofthe heating step, a film-forming step of an insulation film, anannealing step of the copper wiring, or an annealing step of the hardmask made of for example tantalum nitride, may be cited. The highestprocess temperature among the heating steps after the interlayerinsulation films 52 are formed is in general 350° C. to 420° C. However,this invention is also applicable to a case wherein a heat treatmenttemperature after a fluoridation carbon film is formed is 250° C. to350° C., or 200° C. to 300° C.

The hydrogen included in the interlayer insulation films 52 consistingof the fluoridation carbon films may bond fluorine to become hydrogenfluoride (HF) and go off from the films, when the films are heated. As aresult, the films are cavitated and weakened. However, it has been foundthat: when the highest temperature of the heating steps (i.e., thermalhistory of the interlayer insulation films 52) is within the abovetemperature range, if the amount of the hydrogen included in the filmsis 3 atomic % or less, only a smaller amount of the hydrogen fluoridemay go off form the films, so that the films are superior in thermalstability.

Next, a plasma film-forming apparatus that forms an interlayerinsulation film by using a C₅F₈ gas including hydrogen atoms of 1×10⁻³atomic % or less as a source gas is simply explained with referent toFIGS. 3 to 5. In the drawings, 61 represents a processing container(vacuum chamber), and 62 represents a stage including atemperature-adjusting means. The stage 62 is connected to aradio-frequency electric power source 63 of 13.56 MHz for imparting abias, for example.

In an upper portion of the processing container 61, a firstgas-supplying part 64, for example made of alumina, for example having asubstantially cylindrical shape, is provided opposite to the stage 62.Many first gas-supplying holes 65 are formed at a surface opposite tothe stage 62 of the first gas-supplying part 64. The gas-supplying holes65 communicate with a first gas-supplying channel 67 via a gas flowchannel 66. The first gas-supplying channel 67 is connected to asupplying source of an argon (Ar) gas or a krypton (Kr) gas, which is aplasma gas.

A second gas-supplying part 68 consisting of an electric conductor andhaving for example a substantially disk shape is provided between thestage 62 and the first gas-supplying part 64. Many second gas-supplyingholes 69 are formed at a surface opposite to the stage 62 of the secondgas-supplying part 68. For example, as shown in FIG. 4, a lattice-likegas flow channel 71 communicating with the gas-supplying holes 69 isformed inside the second gas-supplying part 68. The gas flow channel 71is connected with the second gas-supplying channel 72. Many openings 73vertically piercing the gas-supplying part 68 are formed in the secondgas-supplying part 68. The openings 73 are formed between adjacentportions of the gas flow channel 71 in order to allow plasma to enter aspace under the second gas-supplying part 68, as shown in FIG. 4, forexample.

Herein, the second gas-supplying part 68 is connected to a supplyingsource of the C₅F₈ gas as a source gas (not shown) via the secondgas-supplying channel 72. Thus, the source gas flows into the gas flowchannel 71 via the second gas-supplying channel 72, and is uniformlysupplied into the space under the second gas-supplying part 68 via thegas-supplying holes 69. In addition, 74 represents a gas-dischargingpipe, which is connected to a vacuuming means 75.

A cover plate 76 consisting of a dielectric material such as alumina isprovided at an upper portion of the first gas-supplying part 64. Anantenna part 77 is provided on the cover plate 76 in such a manner thatthe antenna part 77 is in close contact with the cover plate 76. Asshown in FIG. 5, the antenna part 77 comprises: a circular and flatantenna main body 78 having a lower opening, and a disk-like planeantenna member (slit plate) 79 provided to close the lower opening ofthe antenna main body 78 and having many slits. The antenna main body 78and the plane antenna member 79 are made of an electric conductor, andform a flat and hollow circular waveguide.

A retardation plate 81 consisting of a low-loss dielectric material suchas alumina, silicon oxide or silicon nitride is provided between theplane antenna member 79 and the antenna main body 78. The retardationplate 81 shortens a wavelength of a microwave, which is described below,in order to shorten a guide wavelength in the circular waveguide. Inthis embodiment, the antenna main body 78, the plane antenna member 79and the retardation plate 81 form a radial-line-slit antenna.

In the above antenna part 77, the plane antenna member 79 is mounted onthe processing container 61 via a sealing member not shown in such amanner that the plane antenna member 79 is in close contact with thecover plate 76. Then, the antenna part 77 is connected to an outsidemicrowave generating unit 83 via a coaxial waveguide 82. Thus, forexample, a microwave whose frequency is 2.45 GHz or 84 GHz is suppliedthereto. At that time, an outside waveguide 82A of the coaxial waveguide82 is connected to the antenna main body 78, and a central conductor 82Bis connected to the plane antenna member 79 via an opening formed at theretardation plate 81.

For example, the plane antenna member 79 consists of a copper platehaving a thickness of about 1 mm. As shown in FIG. 5, many slits 84 forgenerating a circularly polarized wave, for example, are formed at theplane antenna member 79. Specifically, a plurality of pairs of slits 84Aand 84B arranged in a substantially T-like shape with a slight gap isformed in a circumferential direction forming a concentric-circlepattern or a spiral pattern or the like. The slits may be arranged in asubstantially V-like shape with a slight gap in each pair. The slits 84Aand 84B are arranged in such a relationship that the slits 84A and 84Bare substantially perpendicular to each other. Thus, a circularlypolarized wave including two perpendicular polarized wave components isradiated. If the pairs of the slits 84A and 84B are arranged accordingto a gap corresponding to a wavelength of the microwave shortened by theretardation plate 81, the microwave is radiated from the plane antennamember 79 as a substantially plane wave.

Next, an example of film-forming process carried out by the abovefilm-forming apparatus is explained. At first, a wafer W as a substrateis conveyed and placed on the stage 62. Then, the inside of theprocessing container 61 is vacuumed to a predetermined pressure, theplasma gas such as an Ar gas is supplied into the first gas-supplyingpart 64 via the first gas-supplying channel 67 at a predetermined flowrate such as 300 sccm, and the source gas such as a C₅F₈ gas is suppliedinto the second gas-supplying part 68 via the second gas-supplyingchannel 72 at a predetermined flow rate such as 150 sccm. Then, theinside of the processing container 61 is maintained at a processpressure of 13.3 Pa, and a surface temperature of the stage 62 is set at350° C.

On the other hand, a radiofrequency wave (microwave) of 2.45 GHz, 2000 Wis supplied from the microwave generating unit 83. The microwave istransmitted in the coaxial waveguide 82 (in the central conductor 82B)in a TM mode, a TE mode or a TEM mode to the plane antenna member 79 ofthe antenna part 77. Then, while the microwave is transmitted radiallyfrom a central portion of the plane antenna member 79 to a peripheralarea thereof, the microwave is radiated from the pairs of the slits 84Aand 84B toward the processing space under the gas-supplying part 64 viathe cover plate 76 and the first gas-supplying part 64.

Then, because of the above arrangement of the pairs of the slits 84A and84B, a circularly polarized wave is uniformly radiated over the surfaceof the plane antenna member 79, so that density of electric field in thespace under the plane antenna member 79 is made uniform. Then, by theenergy of the microwave, uniform plasma with high density, for exampleof an Ar gas, is generated in the space between the first gas-supplyingpart 64 and the second gas-supplying part 68. On the other hand, theC₅F₈ gas ejected from the second gas-supplying part 68 flows into anupper space through the openings 73. Active species generated from theC₅F₈ gas that has been activated by contact with the plasma descend intothe film-forming space under the second gas-supplying part 68 via theopenings 73, and deposit on a surface of the wafer W. Thus, aninterlayer insulation film consisting of a fluoridation carbon film isformed. That is, according to the plasma processing apparatus, thefilm-forming space wherein the active species exist (but no irradiationexists) is formed under the plasma space, so that the fluoridationcarbon film is formed by so-called “soft” active species. Thus, a densethin film with high adhesion and high thermal stability can be obtained.

In the above example, the interlayer insulation film is cited as anexample. However, any other insulation film than the interlayerinsulation film may be adopted. In addition, as a source gas, notlimited to the C₅F₈ gas, a CF₄ gas, a C₂F₆ gas, a C₃F₈ gas, a C₃F₉ gas,a C₄F₈ gas or the like may be used. The ratio (F/C) between fluorine (F)and carbon (C) in the source gas is preferably 1 to 4, more preferably 1to 2. In addition, when the ratio F/C in the fluoridation carbon film issmaller than 0.1, the fluoridation carbon film may have electrostaticproperty. When the ratio F/C in the fluoridation carbon film is largerthan 1.5, adhesion of the fluoridation carbon film may be deteriorated.Thus, the ratio F/C is preferably 0.1 to 1.5, more preferably 0.1 to0.7.

EXAMPLE 1

A fluoridation carbon film having a thickness of 500 nm was formed ontwo bare silicon substrates by conducting a plasma process by means ofthe above plasma film-forming apparatus, by using the C₅F₈ gas as asource gas including hydrogen of 1.17×10⁻³ atomic %. The amount of thehydrogen included in the source gas is a value calculated from an amountof water included therein. The amount of the water was obtained by amass analysis, and the value was 0.5 weight ppm. The process conditionssuch as the flow rate or the electric power were the values as describedabove.

Then, one silicon substrate was heated in a vacuumed container at atemperature rise rate of 10° C./min and a weight of the siliconsubstrate was measured by an electronic balance, so that weightreduction at respective temperatures in a range from a room temperatureto 425° C was obtained. The result is shown in FIG. 6 by a solid line a.

In addition, hydrogen density in the fluoridation carbon film of theother silicon substrate was measured. The result was 3 atomic %. Themeasurement of the hydrogen density was conducted by a Rutherfordscattering spectroscopy. Herein, as described above, the atomic % in thesource gas means the value calculated considering the C₅F₈ as an atom(without dissoluting the C₅F₈ into C and F). The ratio of the C₅F₈ isabout 100%. Thus, for example, if a very small amount of oxygen isincluded in the source gas, the hydrogen density can be deemed a ratioof the number of hydrogen atoms with respect to the number of C₅F₈molecules (the number of assumptive atoms).

On the other hand, the atomic % in the fluoridation carbon film isrepresented by {the number of hydrogen atoms/(the number of hydrogenatoms+the number of carbon atoms+the number of fluorine atoms)}×100.

(Comparison 1)

A fluoridation carbon film having a thickness of 500 nm was formed ontwo bare silicon substrates in the same manner as the example 1 exceptfor by using the C₅F₈ gas as a source gas including hydrogen of15.2×10⁻³ atomic %. The same experiment as the example 1 was conducted,so that weight reduction was examined. The amount of hydrogen includedin the source gas was a value calculated from the amount of waterincluded therein. The amount of water included tberein was 6.5 weightppm. The result is shown in FIG. 6 by a solid line b.

In addition, hydrogen density in the fluoridation carbon film of theother silicon substrate was examined. The result was 5 atomic %.

(Consideration)

As shown in FIG. 6, from the room temperature to about 350° C., theweight reduction was scarcely found in both the fluoridation carbonfilms of the example 1 and the comparison 1. However, at a temperaturehigher than 350° C., the weight reduction was remarkable in the film ofthe comparison 1. On the other hand, in the film of the example 1, thedegree of the weight reduction was small at a temperature lower thanabout 380° C. However, over about 380° C., the weight reduction wasremarkable. However, at a temperature lower than about 420° C., thedegree of the weight reduction was smaller in the film of the example 1than in the film of the comparison 1. In addition, at a temperaturehigher than 425° C., the degree of the weight reduction was large, over10%, in both the films.

That is, when a fluoridation carbon film is subjected to a thermalhistory of 350° C. to 420° C., i.e., when a heating step of heating thefluoridation carbon film to the temperature range is included after thefluoridation carbon film has been formed, the degree of the weightreduction was smaller in the film of the example 1 than in the film ofthe comparison 1. This means that it is possible to raise the processtemperature of the heating step even if the weight reduction has to berestrained under a certain value. In order to obtain a good thin film ina subsequent film-forming step, or in order to improve throughput byshortening the process time, it may often advantageous to raise theprocess temperature. Thus, raising the process temperature isadvantageous in a semiconductor manufacturing step.

As described above, the degree of the weight reduction is smaller in thefluoridation carbon film including the hydrogen whose density is 3atmoic % than in the fluoridation carbon film including the hydrogenwhose density is 5 atmoic %. The reason is thought that only a smallamount of hydrogen fluoride formed by bonding hydrogen and fluorine inthe film goes off from the film. That is, the degassing amount is small.Thus, it is prevented that the film is cavitated, and generation ofwinding of the wirings and/or generation of electro-migration may bereduced. In addition, it is also prevented that the wirings are corrodedby the hydrogen fluoride. Thus, the yield is improved.

If the hydrogen density in the fluoridation carbon film is not higherthan 3.0 atomic % taking into consideration some margin, it is possibleto obtain the above effect sufficiently. For that purpose, it wasconfirmed that it is necessary for the source gas to consist of achemical compound of carbon and fluorine and to include hydrogen atomsof 1×10⁻³ atomic % or less.

Next, an embodiment of the gas for a plasma CVD process according to thepresent invention is explained in detail. The gas for a plasma CVDprocess according to the present invention contains an unsaturatedcarbon fluoride compound and a chemical compound including a hydrogenatom, the amount of the chemical compound including a hydrogen atombeing 90 weight ppm or less.

The unsaturated carbon fluoride compound used for the gas for a plasmaCVD process according to the present invention consists of only carbonatoms and fluorine atoms, and has a double or triple bond. The carbonnumber is preferably 2 to 7, more preferably 2 to 5, further morepreferably 4 to 5, the most preferably 5. Concrete examples of theunsaturated carbon fluoride compound are: an unsaturated carbon fluoridecompound whose carbon number is 2, such as tetrafluoroethylene; anunsaturated carbon fluoride compound whose carbon number is 3, such ashexafluoropropene, tetrafluoropropyne, or tetrafluorocyclopropene; anunsaturated carbon fluoride compound whose carbon number is 4, such ashexafluoro-2-butyne, hexafluoro-1-butyne, hexafluorocyclobutene,hexafluoro-1,3-butadiene, hexafluoro-(1-methylcyclopropene),octafluoro-1-butene, or octafluoro-2-butene; an unsaturated carbonfluoride compound whose carbon number is 5, such asoctafluoro-1-pentyne, octafluoro-2-pentyne, octafluoro-1,3-pentadiene,octafluoro-1,4-pentadiene, octafluorocyclopentene, octafluoroisoprene,hexafluorovinylacetylene, octafluoro-(1-methylcyclobutene), oroctafluoro-(1,2-dimethylcyclopropene); a chemical compound of anunsaturated carbon fluoride whose carbon number is 6, such asdodecafluoro-1-hexene, dodecafluoro-2-hexene, dodecafluoro-3-hexene,decafluoro-1,3-hexadiene, decafluoro-1,4-hexadiene,decafluoro-1,5-hexadiene, decafluoro-2,4-hexadiene,decafluorocyclohexene, hexafluorobenzene, octafluoro-2-hexyne,octafluoro-3-hexyne, octafluorocyclo-1,3-hexadiene, oroctafluorocyclo-1,4-hexadiene; an unsaturated carbon fluoride compoundwhose carbon number is 7, such as undecafluoro-1-heptene,undecafluoro-2-heptene, undecafluoro-3-heptene, ordodecafluorocycloheptene. The preferable one is: tetrafluoroethylene,hexafluoropropene, tetrafluoropropyne, tetrafluorocyclopropene,hexafluoro-2-butyne, hexafluoro-1-butyne, hexafluorocyclobutene,hexafluoro-1,3-butadiene, hexafluoro-(1-methylcyclopropene),octafluoro-1-butene, octafluoro-2-butene, octafluoro-1-pentyne,octafluoro-2-pentyne, octafluoro-1,3-pentadiene,octafluoro-1,4-pentadiene, octafluorocyclopentene, octafluoroisoprene,hexafluorovinylacetylene, octafluoro-1-methylcyclobutene oroctafluoro-1,2-dimethylcyclopropene. The more preferable one is:hexafluoro-2-butyne, hexafluoro-1-butyne, hexafluorocyclobutene,hexafluoro-1,3-butadiene, hexafluoro-(1-methylcyclopropene),octafluoro-1-butene, octafluoro-2-butene, octafluoro-1-pentyne,octafluoro-2-pentyne, octafluoro-1,3-pentadiene,octafluoro-1,4-pentadiene, octafluorocyclopentene, octafluoroisoprene,hexafluorovinylacetylene, octafluoro-(1-methylcyclobutene) oroctafluoro-(1,2-dimethylcyclopropene). The further more preferable oneis octafluoro-2-pentyne, octafluoro-1,3-pentadiene oroctafluorocyclopentene. The further more preferable one isoctafluoro-2-pentyne or octafluorocyclopentene. The most preferable oneis octafluoro-2-pentyne.

The gas for a plasma CVD process according to the present inventioncontains the unsaturated carbon fluoride compound in the amount ofusually 90 weight % or higher, preferably 95 weight % or higher, morepreferably 99 weight % or higher, further more preferably 99.9 weight %or higher. Herein, the gas for a plasma CVD process according to thepresent invention can contain another kind of gas for the plasma CVDprocess and/or a diluent gas as far as the object of the presentinvention is not disturbed. However, it is preferable that the gas for aplasma CVD process doesn't include any other component than theunsaturated carbon fluoride compound.

Regarding the present invention, the chemical compound including ahydrogen atom means an organic compound including a hydrogen atom and aninorganic compound including a hydrogen atom such as water, which existin the gas for a plasma CVD process.

In the gas for a plasma CVD process according to the present invention,the amount of the chemical compound including a hydrogen atom is 90weight ppm or less, preferably 70 weight ppm or less, more preferably 50weight ppm or less, and further more preferably 10 weight ppm or less.In addition, in the gas for a plasma CVD process according to thepresent invention, the amount of the water is preferably 3 weight ppm orless, more preferably 1 weight ppm or less, and further more preferably0.5 weight ppm or less. In a concrete example, when a gas for a plasmaCVD process containing hydrogen atoms in the amount of 1×10⁻³ atomic %or less was used, the amount of hydrogen in a formed film could berestrained to 3 atomic % or less. In the case, the amount of thechemical compound including a hydrogen atom in the gas for a plasma CVDprocess corresponds to the amount of water of 0.5 weight ppm (thecalculated value of the amount of the included hydrogen atoms is1.17×10⁻³ atomic %). Thus, it was conformed that the amount of water inthe gas for a plasma CVD process is preferably 0.5 weight ppm or lower,more preferably 0.1 weight ppm or lower.

When the chemical compound including a hydrogen atom exists in the gasfor a plasma CVD process, the hydrogen atoms are captured in the filmformed by the plasma CVD method. Because of the existence of thehydrogen atoms, for example, a dielectric constant of the film may beraised, reproducibly of the film-formation may be deteriorated, and/or acorrosion gas may be generated when the film is subjected to a heatingprocess. When a semiconductor device is manufactured by using a filmformed by a plasma CVD method as an interlayer insulation film, thesemiconductor device having the interlayer insulation film may besubjected to several heating processes. Then, generation of the hydrogenfluoride may have a great effect on a semiconductor tip itself. Thus, ifthe amount of the chemical compound including a hydrogen atom in the gasfor a plasma CVD process is controlled within the above range, adielectric constant of the film may be decreased, reproducibly of thefilm-formation may be improved, and/or generation of the hydrogenfluoride, which has an adverse effect on the semiconductor tip, may beprevented.

Regarding the amount of the chemical compound including a hydrogen atomin the gas for a plasma CVD process, for example, the amount of anorganic chemical compound including a hydrogen atom may be obtained by agas chromatograph/mass spectro meter, and the amount of water may beobtained by a Karl Fischer moisture meter.

As a method of reducing the amount of the organic chemical compoundincluding a hydrogen atom, a method of removing the organic chemicalcompound by means of an adsorbent, a method of reducing the amount bymeans of distillation, or a method of converting the organic chemicalcompound into another chemical compound that has a large boiling-pointdifference by a chemical reaction and then distilling, may be suitablyselected. The method of removing the organic chemical compound by meansof an adsorbent is preferable. Regarding the water (moisture), a methodwith an adsorbent is preferably used. As an adsorbent used in the methodof reducing the amount of the organic chemical compound including ahydrogen atom, there are described zeolite, molecular sieves 3A,molecular sieves 4A, molecular sieves 5A, molecular sieves 13X, anotherzeolite, alumina, alumina gel, silica, silica gel, activated carbon, orthe like, which has a molecular sieving effect. As the activated carbon,a botanical-series activated carbon made from charcoal, coconut-shellcoal, palm-kernel coal or ash, or a coal-series activated carbon madefrom peat coal, lignite, brown coal, bituminous coal or anthracite coalmay be suitably selected. As an adsorbent used in the method of reducingthe amount of water, there are described molecular sieves 3A, molecularsieves 4A, molecular sieves 5A, molecular sieves 13X, or alumina whichis often used as an adsorbent by a molecular sieving effect. Themolecular sieves 13X is used preferably because the molecular sieves 13Xis superior in removal performance and reduces the organic chemicalcompound including a hydrogen atom at the same time. These adsorbentsare usually burned to be activated under an atmosphere of an inert gassuch as a helium gas at the temperature of 100° C. or higher, preferably200° C. or higher, more preferably 300° C., before usage thereof, inorder to improve the ability of removing the chemical compound includinga hydrogen atom. The burning time of the adsorbent is usually 5 hours orlonger, preferably 10 hours or longer.

The amount of the usage of the adsorbent is preferably 5 to 100 parts byweight, more preferably 10 to 30 parts by weight, with respect to 100parts by weight of the composition of the unsaturated carbon fluoridecompound, and the chemical compound including a hydrogen atom to betreated. If the amount of the usage of the adsorbent is too small, theremoval of the chemical compound including a hydrogen atom tends to beinsufficient. If the amount of the usage of the adsorbent is too large,the manufacturing cost is high.

As a method of bringing the composition of the unsaturated carbonfluoride compound and the chemical compound including a hydrogen atom incontact with the above adsorbent, an immersing method wherein theadsorbent is immersed in a container filled with the composition of theunsaturated carbon fluoride compound and allowed to stand, a flowingmethod wherein the composition of the unsaturated carbon fluoridecompound is caused to flow as a state of gas or liquid through a tubefilled with the adsorbent for contact of the compound and the adsorbent,or any other method may be suitably selected, depending oncharacteristics of the composition of the unsaturated carbon fluoridecompound.

Regarding a method of obtaining the composition of the unsaturatedcarbon fluoride compound and the chemical compound including a hydrogenatom, octafluorocyclopentene is explained as an example. As described inJapanese Patent Laid-Open Publication No. 9-95458, while1,2-dichlorohexafluorocyclopentene is reacted with potassium fluoride indimetylformamide under a flow of a nitrogen gas, the reaction product isextracted from a distillation column connected to the reactingcontainer, so that the octafluorocyclopentene having purity of 99.8 to99.98% may be obtained. The obtained octafluorocyclopentene is preciselydistilled by another distillation column, which has many steps, so thatthe octafluorocyclopentene having moisture of about 30 weight ppm may beobtained.

In addition, octafluoro-2-pentyne may be manufactured by a known methodor a method proposed by the inventors' patent application. According tothe Japanese Patent Application 2001-342791 by the inventors,2,3-dihydrodecafluoropentane and molten potassium hydroxide are broughtin contact with each other, a generated gaseous chemical compound iscaptured in a cooled trap, the captured rough product is preciselydistillated by a distillation column, so that the octafluoro-2-pentynehaving purity of 99.9% or higher may be obtained. When the capturedproduct is precisely distillated, the distillate is captured in a cooledtrap, so that the octafluoro-2-pentyne having moisture of about 20weight ppm may be obtained.

In addition, a minute amount of nitrogen gas and a minute amount ofoxygen gas may exist in the gas for a plasma CVD process according tothe present invention. The total amount of the nitrogen gas and theoxygen gas is preferably 30 volume ppm or lower with respect to thevolume of the gas for a plasma CVD process.

The gas for a plasma CVD process according to the present invention issupplied to a container to conduct a plasma reaction for a semiconductormanufacturing step or the like. In addition, when the plasma reaction isconducted, the gas for a plasma CVD process according to the presentinvention is usually supplied into a plasma CVD apparatus together withan inert gas such as a helium gas, a neon gas, an argon gas, a xenongas, or the like. The inert gas has an effect of diluting the gas for aplasma CVD process and an effect of changing plasma electron temperatureand plasma electron density. Thus, by controlling balance of radicalsand ions in the plasma reaction, suitable film-forming conditions can beobtained. The amount of the inert gas supplied into the plasma CVDapparatus is usually 2 to 100 mol, preferably 5 to 20 mol, with respectto 1 mol of the gas for a plasma CVD process according to the presentinvention.

The CVD process using the gas for a plasma CVD process of the presentinvention is a process wherein the unsaturated carbon fluoride compoundis activated by plasma discharge to generate active species such as ionsand radicals, so that a polymer film of fluorocarbon is formed on asurface of an object to be treated. Regarding the step of forming thepolymer film, it is thought that various reactions such aspolymerization reaction and/or ring-opening reaction of the unsaturatedcarbon fluoride compound are involved complicatedly together with thegeneration of the ion and radical species under an ionization condition,although it is not clear. The object to be treated is not limited, butmay be an object to be used in a semiconductor manufacturing field, anelectric and electronic field and a precise machinery field; or anobject or a surface thereof requiring insulation properties, waterrepellency, corrosion resistance, acid resistance, lubricity,antireflection and/or the like from the point of view of functionalproperties. Especially, the CVD process is suitably used for forming aninsulation film or an insulation material layer in asemiconductor-device manufacturing step, and for forming a protectionfilm of an organic electroluminescence device. The concrete example isan interlayer insulation film on metal wirings made of aluminum, copperor tungsten, or a passivation film for protecting a tip. As the plasmaCVD method, a method described in Japanese Patent Laid-Open PublicationNo. 9-237783 may be used. As a plasma generating condition, usually, ahigh-frequency electric power of 10 W to 10 kW to be applied to an upperelectrode (showerhead) of a parallel-plate system, a temperature of theobject to be treated of 0 to 500° C., and a pressure in a reactionchamber of 0.0133 Pa to 13.3 kPa are adopted. The thickness of thedeposited film is usually 0.01 to 10 μm. The system used for the plasmaCVD process is generally a parallel-plate CVD system, but may be amicrowave CVD system, an ECR-CVD system, an inductively coupled plasma(ICP) CVD system and a high-density plasma CVD system (helicon type,high-frequency-inductive type).

Examples of the gas for a plasma CVD process are explained in detail asfollows. The present invention is not limited to the examples. Herein,if another explanation is not added, “part”, “%”, and “ppm” in theexamples and comparisons mean “part by weight”, “weight %” and “weightppm”, respectively.

The analysis conditions of the following examples and comparisons are asfollows.

<Analysis Condition 1: Gaschromatography Analysis (Abbreviated to “GCAnalysis”) >

Apparatus: HP6890 manufactured by Hewlett Packard Development Company

Column: Ultra Alloy⁺−1(s) (Length 50 m, inner diameter 0.25 mm, filmthickness 1.5 μm)

Column Temperature: fixed at 80° C. for 10 minutes, then heated to 200°C. by the elapse of 20 minutes

Injection Temperature: 200° C.

Carrier Gas: helium (at a flow rate of 1 ml/min)

Detector: FID

Inner Standard Material: n-butane

<Analysis Condition 2: Gaschromatography Mass Analysis (Abbreviated to“GC-MS Analysis”)>

[Gaschromatography Part]

Apparatus: HP6890 manufactured by Hewlett Packard Development Company

Column: Frontier Lab Ultra Alloy⁺−1(s) (60 m×I. D 0.25 mm, 0.4 μmdf)

Column Temperature: −20° C.

Carrier Gas: helium

[Mass Analysis Part]

Apparatus: 5973 NETWORK manufactured by Hewlett Packard DevelopmentCompany

Detector: EI type (acceleration electric voltage: 70 eV)

<Analysis Condition 3: Karl Fischer Moisture Analysis (Abbreviated to“KF Analysis”)>

Apparatus: AQ-7 manufactured by HIRANUMA SANGYO Co., Ltd

Generating Uquid: HYDRANAL Aqualyte RS

Counter Electrode Liquid: Aqualyte CN

Detection Umitation: 0.5 ppm

EXAMPLE 2

Potassium fluoride 30 parts and N,N-dimethylformamide 47 parts weresupplied into a four-opening flask provided with a funnel, adistillation column, a thermometer and an agitating unit, under a flowof a nitrogen gas. A cooling medium of −20° C. was caused to flow into aDimroth condenser provided at the top of the distillation column, and adistillate trap was provided on an atmosphere opening line of thedistillation column, so that the inner temperature of the flask wasraised to 135° C. by the elapse of 0.5 hours.

After the temperature in the flask reaches 135° C.,1,2-dichloro-3,3,4,4,5,5-hexafluorocyclopentene 50.2 parts was addeddropwise from the funnel at a speed of 17.1 parts/hour, so that thereaction was started. After the elapse of 1.5 hours from the start ofthe reaction, it was confirmed that the temperature of a top portion ofthe distillation column was stabled at a boiling point (27° C.) of theproduct, and taking distillate was started. For 3 hours from the startof the distillation, the distillation speed was 0.105 parts/hour. Then,until the temperature of a top portion of the distillation column startsto gradually increase from 27° C. (till the elapse of 5 hours from thestart of the distillation), the distillation speed was 0.105 parts/houror lower. Thus, octafluorocyclopentene 38.24 parts was obtained. Theyield was 87.8%, and the purity obtained by the GC analysis was 99.82%.

Then, the obtained octafluorocyclopentene 38.24 parts and some boilingtips were introduced into a glass round flask, and the flask wasconnected to a Sulzer-PACK distillation column with theoretical platenumber 55 steps. A cooling water of 5° C. was circulated through thecondenser at the top portion of the distillation column, the round flaskwas immersed in an oil bath and the reflux was maintained at 65° C. forone hour. Then, the distillate was taken at a reflux ratio of 40:1, andcaptured by a receiver. Thus, octafluorocyclopentene 34.5 parts wasobtained. The yield was 90.2%, and the purity obtained by the GCanalysis was 99.98%.

In addition, a molecular sieves 13X available in the market was burnedat 350° C. for 12 hours under an atmosphere of a helium gas.

Then, the obtained octafluorocyclopentene 34.5 parts was introduced in astainless-steel container, the above molecular sieves 13X 5.4 parts wasadded thereto, and they were left for one night. After that, theoctafluorocyclopentene was transferred into a stainless-steel cylinderthrough a filter whose hole diameter is 0.05 μm. The cylinder wasconnected to a vacuum line via a valve, the cylinder was cooled byliquid nitrogen, a freeze-degassing process was conducted three times.Thus, a gas for a plasma CVD process was obtained. When the gas for aplasma CVD process in the cylinder was analyzed by the GC-MS analysis,no organic chemical compound having a hydrogen atom was detected (0ppm). In addition, when the gas for a plasma CVD process in the cylinderwas analyzed by the KF analysis, the moisture was lower than thedetection limitation.

EXAMPLE 3

Potassium hydroxide of pellet type (85%) 394 parts, available in themarket, and 1,1,1,2,3,4,4,5,5,5-decafluoropentane (manufactured by DuPont-Mitsui fluorochemical Co., Ltd) 300 parts were introduced in anautoclave made of hastelloy. The contents were sufficiently agitated,and they were reacted on each other at 200° C. for 7.5 hours. Theautoclave was cooled, and connected to a trap for capture and a vacuumpump. Then, the vacuum pump was operated, so that the pressure in theautoclave was reduced, and hence the reaction mixture was discharged andcaptured by the trap that had been cooled by liquid nitrogen. The yieldof the captured products was 182.5 parts. When the captured productswere analyzed by the GC-analysis, octafluoro-2-pentyne,1,1,1,2,4,5,5,5-nonafluoro-2-pentene (abbreviated to “reactionintermediate A”), 1,1,1,3,4,5,5,5-nonafluoro-2-pentene (abbreviated to“reaction intermediate B”) and 1,1,1,2,3,4,4,5,5,5-decafluoropentanewere included in the captured products. With respect to the introducedmaterials, the yield of the final object was 20.6%, and the total yieldof the reaction intermediates A and B was 44.2%.

Then, the obtained captured products 182.5 parts (theoctafluoro-2-pentine: 26.6%, and the total amount of the reactionintermediates A and B: 67.2%) was precisely distilled under a normalpressure by using a distillation column of KS type (with theoreticalplate number 35 steps), manufactured by TOKA SEIKI Co., ltd. Thetemperature of a cooling medium at a top portion of the distillationcolumn was maintained at −5° C. to −10° C. The temperature of thedistillate trap was maintained at −78° C. By the precise distillation,15.0 parts of the distillate of octafluoro-2-pentyne (boilingtemperature: 5° C.) whose purity is 99.6%, 9.4 parts of the distillateof octafluoro-2-pentyne (boiling temperature: 5° C.) whose purity is99.9%, and 89.5 parts of the distillate of reaction intermediates A andB (boiling temperature: 29° C.) whose purity is 99.8% were obtained.

Then, 15.0 parts of the obtained distillate of octafluoro-2-pentynewhose purity is 99.6% and 9.4 parts of the obtained distillate ofoctafluoro-2-pentyne whose purity is 99.9% were mixed, and againprecisely distilled under a normal pressure by using the distillationcolumn of KS type (with theoretical plate number 35 steps), manufacturedby TOKA SEIKI Co., ltd. As a result, 13.0 parts of the distillate ofoctafluoro-2-pentyne (boiling temperature: 5° C.) whose purity is 99.99%was obtained.

In addition, a molecular sieves 13X available in the market was burnedat 350° C. for 12 hours under an atmosphere of a helium gas.

Then, the obtained distillate of octafluoro-2-pentyne 13.0 parts(boiling temperature: 5° C.) were introduced in a stainless-steelcontainer, the above molecular sieves 13X 2.6 parts was added thereto,and they were left for one night. After that, the octafluoro-2-pentynewas transferred into a stainless-steel cylinder through a filter whosehole diameter is 0.05 μm. The cylinder was connected to a vacuum linevia a valve, the cylinder was cooled by liquid nitrogen, and afreeze-degassing process was conducted three times. Thus, a gas for aplasma CVD process was obtained. When the gas for a plasma CVD processin the cylinder was analyzed by the GC-MS analysis, no organic chemicalcompound having a hydrogen atom was detected (0 ppm). In addition, whenthe gas for a plasma CVD process in the cylinder was analyzed by the KFanalysis, the moisture was lower than the detection limitation.

(Comparison 2)

Instead of using the 5.4 parts of the molecular sieves 13X that had beenburned at 350° C. for 12 hours under an atmosphere of a helium gas, 2.7parts of a molecular sieves 13X available in the market was used as itwas. Except for that, the same conditions as the example 2 were adopted,so that a gas for a plasma CVD process was obtained in thestainless-steel cylinder. When the gas for a plasma CVD process in thecylinder was analyzed by the GC-MS analysis, the total amount of organicchemical compounds having a hydrogen atom was 150 ppm with respect tothe weight of the gas for a plasma CVD process. In addition, when thegas for a plasma CVD process in the cylinder was analyzed by the KFanalysis, the moisture was 5 ppm with respect to the weight of the gasfor a plasma CVD process.

(Comparison 3)

Instead of using the 2.6 parts of the molecular sieves 13X that had beenburned at 350° C. fo 12 hours under an atmosphere of a helium gas, 2.6parts of an unprocessed molecular sieves 13X was used. Except for that,the same conditions as the example 2 were adopted, so that a gas for aplasma CVD process was obtained in the stainless-steel cylinder. Whenthe gas for a plasma CVD process in the cylinder was analyzed by theGC-MS analysis, the following organic chemical compounds having ahydrogen atom were found therein; monofluoroacetylene of 20.5%,pentafluoroethane of 3.5%, 1,1-dihydrotetrafluoropropene of 20%, and3,3,3-trifluoropropyne of 56%. The total amount of them was 130 ppm withrespect to the weight of the gas for a plasma CVD process. In addition,when the gas for a plasma CVD process in the cylinder was analyzed bythe KF analysis, the moisture was 6 ppm with respect to the weight ofthe gas for a plasma CVD process.

EXAMPLE 4

A film was formed by a plasma CVD process using the gas for a plasma CVDprocess manufactured according to the example 2.

A silicon oxide film wafer on which aluminum has been partiallyvapor-deposited was used as a substrate. A parallel-plate type of plasmaCVD apparatus was used as the plasma CVD apparatus. The gas for a plasmaCVD process manufactured according to the example 2 was used. Then, aplasma CVD process for forming an insulation film was conducted underthe following conditions; a flow rate of the gas for a plasma CVDprocess: 40 sccm, a flow rate of the argon gas: 400 sccm, a pressure:250 mTorr, an RF output (frequency: 13.56 MHz): 400 W, and a temperatureof the substrate: 260° C.

A film having a thickness of 0.5 μm was obtained on the substrate by theabove process under the above conditions. No void was generated in thefilm, and the film was dense and uniform. Adhesion of the film to thesubstrate was also good. The dielectric constant of the film was 2.2.When the silicon wafer on which the film had been formed was placed in avacuum container and subjected to a heating process of 400° C. under areduced pressure, generation of hydrogen fluoride was not found.

EXAMPLE 5

The gas for a plasma CVD process manufactured according to the example 3was used instead of the gas for a plasma CVD process manufacturedaccording to the example 2. Except for that, the same experiment as theexample 4 was conducted so that a film having a thickness of 0.4 μm wasobtained on the substrate. No void was generated in the film, and thefilm was dense and uniform. Adhesion of the film to the substrate wasalso good. The dielectric constant of the film was 1.8. When the siliconwafer on which the film had been formed was placed in a vacuum containerand subjected to a heating process of 400° C. under a reduced pressure,generation of hydrogen fluoride was not found.

(Comparison 4)

The gas for a plasma CVD process manufactured according to thecomparison 2 was used instead of the gas for a plasma CVD processmanufactured according to the example 2. Except for that, the sameexperiment as the example 4 was conducted so that a film having athickness of 0.5 μm was obtained on the substrate. No void was generatedin the film, and the film was dense and uniform. Adhesion of the film tothe substrate was also good. The dielectric constant of the film was2.4. However, when the silicon wafer on which the film had been formedwas placed in a vacuum container and subjected to a heating process of400° C. under a reduced pressure, generation of hydrogen fluoride wasfound by the GC-MS analysis.

(Comparison 5)

The gas for a plasma CVD process manufactured according to thecomparison 2 was used instead of the gas for a plasma CVD processmanufactured according to the example 3. Except for that, the sameexperiment as the example 3 was conducted so that a film having athickness of 0.4 μm was obtained on the substrate. No void was generatedin the film, and the film was dense and uniform. Adhesion of the film tothe substrate was also good. The dielectric constant of the film was2.0. However, when the silicon wafer on which the film had been formedwas placed in a vacuum container and subjected to a heating process of400° C. under a reduced pressure, generation of hydrogen fluoride wasfound by the GC-MS analysis.

The results of the examples 4-5 and the comparisons 4-5 are shown inTable 1. It can be found from Table 1 that the gas for a plasma CVDprocess containing the unsaturated carbon fluoride and the chemicalcompound including a hydrogen atom, the amount of the chemical compoundincluding a hydrogen atom being 90 weight ppm or less, can be obtainedby the manufacturing method of the present invention. In addition, inthe example 4 or 5 wherein the gas for a plasma CVD process of thepresent invention was used, the dielectric constant of the film formedby the CVD process was reduced, and generation of the hydrogen fluoride,which is a corrosion gas, was restrained. TABLE 1 AMOUNT OF AMOUNT OFORGANIC CHEMICAL CARBON CHEMICAL COMPOUND COMPOUND FLUORIDE INCLUDINGHYDROGEN INCLUDING DIELECTRIC GENERATION COMPOUND ATOM MOISTURE HYDROGENATOM CONSTANT OF HF GAS EXAMPLE 4 OCTAFLUORO -  0 ppm 0.5 ppm 0.5 ppm orLESS 2.2 NOT FOUND CYCLO PENTENE or LESS EXAMPLE 5 OCTAFLUORO −2 -  0ppm 0.5 ppm 0.5 ppm or LESS 1.8 NOT FOUND PENTYNE or LESS COMPARISON 4OCTAFLUORO - 160 ppm   5 ppm 155 ppm 2.4 FOUND CYCLO PENTENE COMPARISON5 OCTAFLUORO −2 - 130 ppm   6 ppm 138 ppm 2.0 FOUND PENTYNE(NOTE)DETECTION LIMITATION OF MOISTURE: 0.5 ppm

1. A semiconductor device comprising an insulation film consisting of afluoridation carbon film that has been subjected to thermal history of420° C. or lower, wherein an amount of hydrogen atoms included in thefluoridation carbon film is 3 atomic % or less before the fluoridationcarbon film is subjected to the thermal history.
 2. A semiconductordevice according to claim 1, wherein the insulation film is aninterlayer insulation film.
 3. A manufacturing method of a semiconductordevice comprising the steps of: generating a plasma of a source gasconsisting of a chemical compound of carbon and fluorine and includinghydrogen atoms of 1×10⁻³ atomic % or less, and forming an insulatingfilm consisting of a fluoridation carbon film that includes hydrogenatoms of 3 atomic % or less, on a substrate, by using the plasma of thesource gas.
 4. A manufacturing method of a semiconductor deviceaccording to claim 3, further comprising: heating the substrate at atemperature of 420° C. or lower, after the step of forming theinsulating film.
 5. A manufacturing method of a semiconductor deviceaccording to claim 3 or 4, wherein the chemical compound of carbon andfluorine is C₅F₈.
 6. A gas for a plasma CVD process, comprising anunsaturated carbon fluoride compound and a chemical compound including ahydrogen atom, the amount of the chemical compound including a hydrogenatom being 90 weight ppm or less.
 7. The gas for the plasma CVD processaccording to claim 6, wherein the amount of the chemical compoundincluding a hydrogen atom is 10 weight ppm or less.
 8. The gas for theplasma CVD process according to claim 6, further comprising water in theamount of 3 weight ppm or less.
 9. The gas for the plasma CVD processaccording to any of claims 6 to 8, wherein the unsaturated carbonfluoride compound is octafluorocyclopentene, hexafluoro-2-pentyne, orhexafluoro-1,3-butadiene.
 10. A manufacturing method of the gas for theplasma CVD process according to any of claims 6 to 8, comprising thestep of bringing a composition of an unsaturated carbon fluoridecompound and a chemical compound including a hydrogen atom in contactwith burned adsorbent.
 11. A forming method of an insulation filmcomprising the step of: conducting a plasma CVD process by using the gasfor the plasma CVD process according to any of claims 6 to
 8. 12. A gasfor a plasma CVD process, comprising an unsaturated carbon fluoridecompound, and hydrogen atoms in the amount of 1×10⁻³ atomic % or lower.13. A gas for a plasma CVD process, comprising an unsaturated carbonfluoride compound, and water in the amount of 0.5 weight ppm or less.14. The gas for the plasma CVD process according to claim 13, whereinthe amount of water is 0.1 weight ppm or less.